Semiconductor device with a field stop zone and process of producing the same

ABSTRACT

Embodiments discussed herein relate to processes of producing a field stop zone within a semiconductor substrate by implanting dopant atoms into the substrate to form a field stop zone between a channel region and a surface of the substrate, at least some of the dopant atoms having energy levels of at least 0.15 eV below the energy level of the conduction band edge of semiconductor substrate; and laser annealing the field stop zone.

TECHNICAL FIELD

The subject matter disclosed herein generally relates to thesemiconductor devices and processes for making them, and morespecifically, to an insulated gate bipolar transistors, IGBTs, withfield stop zones.

BACKGROUND INFORMATION

IGBTs have been made as punch-through devices (PT-IGBT) in which a DMOStype structure is formed at the top of an epitaxially deposited siliconsubstrate. The epitaxial layer is formed atop a higher concentrationbuffer layer, of the same conductivity type, which is in turn formed ona substrate of opposite conductivity type and which acts as a minoritycarrier injection source. In such punch-through devices, the electricfield across the silicon substrate under reverse bias reaches from thetop surface of the silicon to the buffer layer, which also acts as adepletion layer stop.

Field stop IGBTs, on the other hand, are made starting from a low dopedsubstrate of a first conductivity type without employing epitaxiallayers. The field stop zone has considerably lower doping concentrationthan the buffer layer in a PT-IGBT.

The field stop zone plays a key role in the operational properties ofIGBTs. In particular, thickness and concentration of the field stop zonegreatly affect the switching and breakdown voltage characteristics ofthe device.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 illustrates a cross-sectional view of a few cells of aconventional IGBT showing a field stop zone that is located adjacent tothe collector electrode;

FIG. 2 illustrates an example of a dopant profile of the IGBT shown inFIG. 1;

FIG. 3 illustrates a cross-sectional view of an embodiment of theinvention comprising a first field stop zone adjacent to the p⁺-zone andsingle further or second field stop zone;

FIG. 4 illustrates an example of a dopant profile of the IGBTembodiments shown in FIG. 3;

FIG. 5 illustrates a cross-sectional view of some embodiments of theinvention comprising a first field stop zone adjacent to the p⁺-zone andtriple further or second field stop zones of different concentration;

FIG. 6 illustrates some embodiments of a dopant profile of the IGBTembodiments shown in FIG. 5; and

FIG. 7 illustrates an example of a semiconductor diode comprising fieldstop zones.

DETAILED DESCRIPTION

The following detailed description refers to the accompanying drawingsthat show, by way of illustration, specific details and embodiments inwhich the invention may be practiced. These embodiments are described insufficient detail to enable those skilled in the art to practice theinvention. Other embodiments may be utilized and structural, logical,and electrical changes may be made without departing from the scope ofthe invention. The various embodiments are not necessarily mutuallyexclusive, as some embodiments can be combined with one or more otherembodiments to form new embodiments.

In the following description, the terms “wafer” and “substrate” may beused interchangeably to refer generally to any structure on whichintegrated circuits are formed and also to such structures duringvarious stages of integrated circuit fabrication. The term “substrate”is understood to include a semiconductor wafer. The term “substrate” isalso used to refer to semiconductor structures during processing and mayinclude other layers that have been fabricated thereupon. Both “wafer”and “substrate” include doped and undoped semiconductors, epitaxialsemiconductor layers supported by a base semiconductor or insulator, aswell as other semiconductor structures well known to one skilled in theart.

The term “conductor” is understood to generally include n-type andp-type semiconductors and the term “insulator” or “dielectric” isdefined to include any material that is less electrically conductivethan the materials referred to as “conductors.” The following detaileddescription is, therefore, not to be taken in a limiting sense.

The conventional IGBT and its dopant profile as mentioned further aboveis shown in FIG. 1 and FIG. 2, respectively.

FIG. 1 illustrates a partial cross-sectional view of cells of aconventional IGBT comprising a thin semiconductor substrate 1, a baseregion 2 embedded in a top main surface of said substrate 1, and asource region 3 formed within said base region 2. A gate 4 that isembedded in an insulating silicon oxide layer 5 is formed atop said baseand source region 2 and 3, respectively. An electrode 6 is formed oversaid top main surface of said substrate 1 contacting said base andsource region 2 and 3, respectively. A p⁺-region 7 is formed in saidsubstrate 1 adjacent to a bottom main surface, and a field stop zone 8is formed in said substrate 1 adjacent to said p⁺-region. A collectorelectrode 9 is formed atop said bottom main surface of said substrate 1.The collector electrode 9 may consist of a plurality of differentconducting layers.

FIG. 2 illustrates an example of a dopant profile of the IGBT describedabove and, in particular, of the field stop zone 8. Here, said fieldstop zone 8 comprises a plurality of sequential implants (NH3, NH2, NH1)that function as a buffer layer.

Conventionally, a field stop zone is formed within a substrate bythinning the substrate to a precise thickness, implanting an n-typedopant such as phosphorus or arsenic into the bottom surface of thesubstrate, followed by high temperature anneal (usually greater thanabout 800° C.) to activate the dopant. It is also known to use multipleproton implantations in order to produce a field stop zone. In suchprocesses, hydrogen is implanted into a predetermined depth of thesubstrate, where the hydrogen atoms function as n-dopants in combinationwith the implant damage.

FIG. 3 illustrates some embodiments of an IGBT comprising a thinsemiconductor substrate 10, a base region 11 embedded in a top surfaceof said substrate 10 and a source region 12 formed within said baseregion 11. A gate 13 that is embedded in an insulating silicon oxidelayer 14 is formed atop said base and source regions 11 and 12,respectively. An electrode 15 is then formed over said top surface ofsaid substrate 10 contacting said base- and source regions 11 and 12,respectively. A p-doped zone 16 is formed in said substrate 10 adjacentto a bottom surface and a first field stop zone 17 of deep is formed ofdeep donor dopants in said substrate 10 adjacent to said p-emitter 16. Asecond field stop zone 18 is formed between said first field stop zone17 and said top surface of said substrate 10. A metal electrode 19 isformed atop said bottom main surface of said substrate 10.

Here, in some embodiments the first field stop zone 17 is produced byimplanting selenium atoms through said bottom main surface of saidsubstrate 10 and annealing said selenium atoms using laser annealingmeans. Small particles lying on the surface during selenium implantationare irrelevant to causing potential defects in the first field stop zone17, because the laser-annealing process ensures sufficient lateraldiffusion of the selenium atoms resulting in an undamaged first fieldstop zone 17 and with it in low leakage currents.

In some embodiments, various other deep donor dopant atom types such assulphur atoms having energy levels of at least 0.15 eV below the energylevel of the conduction band edge of the semiconductor substrate 10. Insome embodiments, for a silicon substrate, sulfur atoms in particular,can be used instead of selenium atoms.

Moreover, selenium atoms constitute deep donors within the siliconsubstrate 10 and are not electrically activated within the space-chargeregion until a specific time period passed, enabling the space-chargeregion to respond much faster to short circuits than the conventionalfield stop zones produced by diffusion of implanted phosphorus or protonimplantation. Thus, holes can be injected fast from the p-doped emitter16 to compensate for the change of the electric field caused by apotential short circuit.

The reasons mentioned above are also responsible for the fasterswitch-on speed of the IGBT. A second field stop zone 18, produced bymeans of proton implantation and subsequent thermal annealing attemperatures equal or less than 420° C., further promotes soft switchingproperties of the IGBT.

In some embodiments, the field stop zone closest to the back surface ofthe substrate is formed in such that its main dopant peak is located asclose to the p-emitter zone of the IGBT as possible, in order to ensuresufficient short circuit withstandability.

In an embodiment of the invention, the dopant atoms additionallycomprise a second type of dopant atoms, e.g. atoms acting as shallowdonor impurities. Such atoms, which may be phosphorus or, alternatively,arsenic atoms, in combination with the selenium or sulphur atoms resultin an approximately temperature-independent switching characteristics ofa semiconductor device formed in the semiconductor substrate. Inparticular, in such semiconductor device a reasonable balance betweensoftness of the turn-off characteristics and switching losses across thewhole operating temperature range of the device may be obtained. Toachieve this, the ratio between the dopant doses of both types of atomsis suitably controlled. In some embodiments, the ratio is in the rangebetween about 0.15 and about 0.8. In some embodiments, the ratio isbetween about 0.3 and about 0.7.

In some embodiments using a thin semiconductor substrates (having athickness of e.g. 200 μm or below), laser annealing means for annealingthe implantation zone are used. In other embodiments, using a relativelythick semiconductor substrate (e.g. above 200 μm), a thermal annealingis used. In some embodiments, combining selenium or sulphur dopant atomson the one hand with phosphorus or arsenic dopant atoms on the other,for annealing either type of dopant atoms, annealing using a laser isperformed.

The p-doped zone 16 can be produced by implantation of boron atoms incombination with a second laser-annealing step. The laser power of thesecond laser annealing step should, however, be lower than the powerused for producing said first field stop zone 17 in order to preventboron atoms to be deposited deeply within the silicon substrate 10.Alternatively, the p-doped zone 16 produced by implanted boron atoms canalso be activated sufficiently by a conventional thermal annealing stepat temperatures below 420° C.

The laser-annealing step results in an approximately rectangular boronor selenium atom concentration profile, also characterized as “box”profile. Here, the maximum achievable dopant concentration is determinedby the solubility of the respective elements in the molten silicon. Insome embodiments, a maximum dopant concentration need not be reachedbecause a dopant dose that is greater than 5×10¹¹ cm⁻², morespecifically greater than 2×10¹² cm⁻², for the field stop zone 17,located adjacent to the p-doped zone 16, is sufficient.

The penetration depth of the field stop zone 17 is determined by thelaser energy during the laser-annealing step. In some embodiments,depths are in the range of less than 1 μm. In some embodiments, depthsare in the range of less than 0.5 μm. In some embodiments, the fieldstop zone closest to the back surface of the substrate should be formedin such a way that its main dopant peak is located as close to thep-emitter zone of the IGBT as possible in order to ensure sufficientshort circuit withstandability.

A embodiments of the present invention include the combination of adopant atom field stop, wherein at least part of the dopant atoms areatoms with an energy level that is at least 0.15 eV below the energylevel of the conduction band edge of the semiconductor, whereby theseatoms are activated by laser annealing, and—in some embodiments—a protoninduced field stop within a semiconductor device e.g. an IGBT or adiode. The resulting higher degree of freedom allows adjusting the shortcircuit withstandability, the switch-on properties and the softness ofthe switch-off properties of the IGBT. It also minimizes IGBT leakagecurrent.

In some embodiments, the field stop zone is at least partly defined byimplanted selenium atoms. The advantage of using selenium atoms is thatthey constitute deep donors with an energy level at least 0.15 eV belowthe energy level of the conduction band edge within a siliconsemiconductor substrate, and are only fully activated electricallywithin the space-charge region after a specific time delay. In suchembodiments, the space-charge region response to any short circuitsituations is faster.

In some embodiments, the field stop zone is at least partly defined byimplanted sulphur atoms. The advantage of using sulphur atoms is thatthey have an energy level that is at least 0.15 eV below the energylevel of the conduction band edge of the semiconductor substrateproviding properties that are similar to selenium atoms.

In some embodiments, the dopant dose of said field stop zone is at least5×10¹¹ cm⁻², preferably 2×10¹² cm⁻² or more. The laser annealing processleads to the formation of an approximately rectangular concentrationprofile of said selenium or sulphur atoms within the semiconductorsubstrate and enables a much higher activation degree of the implantedSe or S atoms compared to a conventional activation or diffusion processperformed in furnaces.

Furthermore, the depth of penetration of said field stop zone is lessthan 1 μm with respect to the second main surface of said semiconductorensuring a sufficient short circuit withstandability of thesemiconductor.

In other embodiments of the present invention, the thermal annealing ofthe second field stop zone is carried out at a temperature that is equalto or less than 420° C. in order to activate the implanted protons ofsaid second field stop zone and, in some embodiments, the boron atoms ofthe emitter zone without causing a significantly increased depth ofpenetration within the semiconductor substrate and reducing anypossibility of damage to metal contacts.

FIG. 4 shows an example of some embodiments of a possible dopant profileof the IGBT as illustrated in FIG. 3. A first peak 20 represents thedopant concentration of the p-doped zone 16, the second peak 21represents the dopant concentration of the first field stop zone 17 thatis produced by selenium implantation and subsequent laser annealing, andthe third peak 22 represents the dopant concentration of the secondfield stop zone 18 that is produced by proton implantation.

FIG. 5 illustrates some embodiments of an IGBT comprising asemiconductor substrate 23, a base region 24 embedded in a top mainsurface of said substrate 23, and a source region 25 formed within saidbase region 24. A gate 26 that is embedded in an insulating siliconoxide layer 27 is formed above said base and source region 24 and 25,respectively. An electrode 28 is then formed over said top surface ofsaid substrate 23 contacting said base and source region 24 and 25,respectively.

In some embodiments, a p-doped zone 29 is formed in said substrate 23 byboron implantation adjacent to a bottom main surface of said substrate23, and a first field stop zone 30 is formed in said substrate 23 byselenium implantation adjacent to said p-doped zone 29. In someembodiments, three second field stop zones 31 of different dopantconcentrations are formed between said first field stop zone 30 and saidtop main surface of said substrate 23 at different depths ofpenetration, for example, by proton implantation, at different energylevels. A metal electrode 32 is formed atop said bottom main surface ofsaid substrate 23.

FIG. 6 shows a dopant profile of some embodiments of the IGBTillustrated in FIG. 5. A first peak 33 represents the dopantconcentration of the p-doped zone 29, a second peak 34 represents thedopant concentration of the first field stop zone 30 that is produced byselenium implantation and subsequent laser annealing, and threesubsequent peaks 35 represent the dopant concentration of the threesecond field stop zones 31 that are produced by proton implantation atdifferent depths of penetration and subsequent thermal annealing attemperatures below 420° C.

FIG. 7 schematically illustrates some embodiments of a semiconductordiode 36 comprising a first semiconductor layer 38 of n-type, a secondsemiconductor layer 37 of p-type conductivity and corresponding metalcontacts 39 and 40 on a top and bottom main surface of saidsemiconductor layers 37 and 38. The semiconductor layer 38 furthercomprises a field stop zone 42 and—in some embodiments, as illustrated—afurther field stop zone 41. The field stop zone 42 is produced e.g. byselenium implantation and laser annealing. An n⁺ emitter zone 43 isprovided in the second main surface of the substrate and produced, e.g.by phosporus implantation and laser annealing. In some embodiments, thefurther field stop zone 41 is produced in a conventional manner, bymeans of proton implantation.

The field stop zones 42 and 41 reduce the tendency to currentfilamentation caused by thermomigration of the metal contacts 39, 40 ofsaid semiconductor diode 36, which could lead for example to a distortedoff-state characteristic curve of the semiconductor device.

The process is, in some embodiments, a process of producing a field stopzone within a semiconductor substrate comprising a first main surfaceand a second main surface, wherein the first main surface is forarranging electronic element structures therein and thereon and thesecond main surface is opposed to the first main surface, comprising thesteps of implantation of dopant atoms through said second main surface,at least part of said dopant atoms having an energy level that is atleast 0.15 eV below the energy level of the conduction band edge of saidsemiconductor, e.g. selenium or sulphur atoms, and annealing said fieldstop zone using laser annealing means and/or thermal annealing means.

In some embodiments of the process improved performance is attained by aprocess of manufacturing a semiconductor device comprising at least afirst field stop zone of a first conductivity type defined by implantedfirst dopant atoms and a second field stop zone of the firstconductivity type defined by implanted protons as second donator atoms,the process comprising: producing a metal layer pattern on a first mainsurface of a semiconductor substrate of said semiconductor device,producing said first field stop zone with a first dopant concentrationby dopant implantation in said semiconductor substrate using said firstdopant atoms, said first dopant atoms having an energy level that is atleast 0.15 eV below the energy level of the conduction band edge of saidsemiconductor substrate, and annealing said first field stop zone usinglaser annealing means.

In some embodiments, the dopant atoms in the first field stop zoneadditionally comprise a further type of dopant atoms acting as shallowimpurities like e.g. phosphorus atoms. Subsequently, for bothaforementioned embodiments, the steps of producing a p⁺-zone of a secondconductivity type on a second main surface of said semiconductorsubstrate, the second main surface being opposed to the first mainsurface, producing said second field stop zone of said firstconductivity type and a second dopant concentration byproton-implantation between said first field stop zone and said firstmain surface of said semiconductor substrate, annealing said secondfield stop zone using thermal annealing means, and forming a backsidemetallization connected to and across said second main surface of saidsemiconductor substrate are carried out.

In some embodiments, the apparatus discussed is a semiconductor devicecomprising a semiconductor substrate of a first conductivity typecomprising a first and second main surface, the second main surfacebeing opposite to the first main surface; an MOS-structure formed in thesemiconductor substrate adjacent to that first main surface, a metallayer pattern on said first main surface, a zone of a secondconductivity type formed adjacent to said second main surface, a firstfield stop zone of said first conductivity type, defined by implantedfirst dopant atoms of a first dopant concentration and formed adjacentto said zone adjacent to said second main surface, at least part of saidfirst dopant atoms having an energy level that is at least 0.15 eV belowthe energy level of the conduction band edge of said semiconductorsubstrate, a second field stop zone of a first conductivity type definedby implanted protons of said second dopant concentration and formedbetween said first field stop zone and said first main surface, and abackside metallization connected to and across said second main surfaceof said semiconductor substrate.

In addition, advantages of the present invention are attained by anotherembodiment of the invention which is a semiconductor diode, comprising afirst semiconductor layer of a first conductivity type and a secondsemiconductor layer of a second conductivity type, and furthercomprising a first field stop zone of said first conductivity typedefined by implanted dopant atoms having an energy level that is atleast 0.15 eV below the energy level of the conduction band edge of saidfirst semiconductor layer, whereby these implanted atoms are activatedby laser annealing.+++

The accompanying drawings that form a part hereof show by way ofillustration, and not of limitation, specific embodiments in which thesubject matter may be practiced. The embodiments illustrated aredescribed in sufficient detail to enable those skilled in the art topractice the teachings disclosed herein. Other embodiments may beutilized and derived therefrom, such that structural and logicalsubstitutions and changes may be made without departing from the scopeof this disclosure. This Detailed Description, therefore, is not to betaken in a limiting sense, and the scope of various embodiments isdefined only by the appended claims, along with the fall range ofequivalents to which such claims are entitled.

Such embodiments of the inventive subject matter may be referred toherein, individually and/or collectively, by the term “invention” merelyfor convenience and without intending to voluntarily limit the scope ofthis application to any single invention or inventive concept if morethan one is in fact disclosed. Thus, although specific embodiments havebeen illustrated and described herein, it should be appreciated that anyarrangement calculated to achieve the same purpose may be substitutedfor the specific embodiments shown. This disclosure is intended to coverany and all adaptations or variations of various embodiments.Combinations of the above embodiments, and other embodiments notspecifically described herein, will be apparent to those of skill in theart upon reviewing the above description.

The Abstract of the Disclosure is provided to comply with 37 C.F.R.§1.72(b), requiring an abstract that will allow the reader to quicklyascertain the nature of the technical disclosure. It is submitted withthe understanding that it will not be used to interpret or limit thescope or meaning of the claims. In addition, in the foregoing DetailedDescription, it can be seen that various features are grouped togetherin several embodiments for the purpose of streamlining the disclosure.This method of disclosure is not to be interpreted as reflecting anintention that the claimed embodiments require more features than areexpressly recited in each claim. Rather, as the following claimsreflect, inventive subject matter lies in less than all features of asingle disclosed embodiment. Thus the following claims are herebyincorporated into the Detailed Description, with each claim standing onits own as a separate embodiment.

1. A process of producing a field stop zone within a semiconductorsubstrate having semiconductor elements formed at a top main surfacethereof, implanting dopant atoms into a bottom main surface of thesubstrate to form a field stop zone between a channel region and thebottom main surface of the substrate, at least some of the dopant atomshaving energy levels of at least 0.15 eV below the energy level of theconduction band edge of semiconductor substrate; and laser annealingsaid field stop zone.
 2. The process according to claim 1, wherein saiddopant atoms comprise selenium atoms.
 3. The process according to claim1, wherein said dopant atoms comprise sulphur atoms.
 4. The processaccording to claim 1, wherein implanting dopant atoms also includesimplanting other dopant atoms, which act as shallow impurities, in afurther implantation zone.
 5. The process according to claim 4, whereinthe other dopant atoms comprise phosphorus atoms.
 6. The processaccording to claim 4, wherein the other dopant atoms comprise arsenicatoms.
 7. The process according to claim 4, also including selecting adopant dose ratio between dopant atoms having an energy level that is atleast 0.15 eV below the energy level of the conduction band edge andother dopant atoms which act as shallow impurities, to obtain anapproximately temperature-independent softness during turn-off acrossthe operating temperature range of a semiconductor device formed withinsaid semiconductor substrate.
 8. The process according to claim 7,wherein the dopant dose ratio is in the range between about 0.15 and0.8.
 9. The process according to claim 4, comprising thermally annealingthe further field stop zone.
 10. The process according to claim 1,wherein a dopant dose of said field stop zone is greater than about5×10¹¹ cm⁻².
 11. The process according to claim 1, wherein implantingdopant atoms forms a field stop zone at a depth of penetration that isless than 1 μm from the surface of the substrate.
 12. A process ofmanufacturing a semiconductor device, comprising: implanting a firstdopant through a first surface in a semiconductor substrate using firstdopant atoms, at least part of said first dopant atoms having an energylevel that is at least 0.15 eV below the energy level of the conductionband edge of said semiconductor substrate to produce a first field stopzone of a first conductivity type with a first dopant concentration;performing at least one of laser annealing or thermal annealing of saidfirst field stop zone; implanting a second dopant to produce a secondfield stop zone of said first conductivity type and a second dopantconcentration by proton-implantation between said first field stop zoneand a further surface of said semiconductor substrate, the furthersurface opposed to the first surface; and thermal annealing said secondfield stop zone.
 13. The process according to claim 12, wherein prior toimplanting the dopant in an initial step, forming a semiconductor devicestructure upon the further surface of said semiconductor substrate, andsubsequent to annealing said second field stop zone, forming a backsidemetallization on the first substrate surface.
 14. The process accordingto claim 12, wherein said thermal annealing is carried out at atemperature that is equal to or less than about 420° C.
 15. The processaccording to claim 12, wherein said first field stop zone is produced byimplantation of selenium atoms.
 16. The process according to claim 12,wherein said first field stop zone is produced by implantation ofsulphur atoms.
 17. The process according to claim 12, wherein said thefirst dopant atoms are selenium or sulphur atoms, and the second dopantis phosphorus or arsenic atoms.
 18. The process according to claim 17,wherein the ratio between selenium or sulphur atoms, respectively, andphosphorus or arsenic atoms, respectively, is adjusted to be within arange between about 0.15 and 0.8.
 19. The process according to claim 12,also comprising forming an emitter zone of the second conductivity typein the further surface by implantation of boron atoms.
 20. The processaccording to claim 12, also comprising laser annealing said emitterzone.
 21. The process according to claim 12, wherein said first dopantdose of said first field stop zone is about at least 5×10¹¹ cm⁻². 22.The process according to claim 12, wherein implanting said first dopantforms said first field stop zone at a depth of penetration that is lessthan 1 μm with respect to said further surface.
 23. A semiconductordevice comprising: a semiconductor substrate of a first conductivitytype comprising a first and second main surface, the second main surfacebeing opposite to a first main surface; an implantation zone patternbeing formed in that first main surface; an emitter zone of a secondconductivity type formed adjacent to a second main surface; a firstfield stop zone of said first conductivity type defined by implantedfirst dopant atoms with a first dopant dose and formed adjacent to saidemitter zone in said semiconductor substrate, at least part of saidfirst dopant atoms having an energy level that is at least 0.15 eV belowthe energy level of the conduction band edge of said semiconductorsubstrate; and a second field stop zone of a first conductivity typedefined by implanted protons of said second dopant concentration andformed between said first field stop zone and said first main surface.24. The semiconductor device according to claim 23, wherein said firstfield stop zone comprises implanted selenium atoms.
 25. Thesemiconductor device according to claim 23, wherein said first fieldstop zone comprises implanted sulphur atoms.
 26. The semiconductordevice according to claim 23, wherein said dopant atoms also compriseatoms which act as shallow impurities.
 27. The semiconductor deviceaccording to claim 26, wherein said first field stop zone comprisesimplanted phosphorus atoms.
 28. The semiconductor device according toclaim 26, wherein said first field stop zone comprises implanted arsenicatoms.
 29. The semiconductor device according to claim 23, wherein saidemitter zone comprises implanted boron atoms.
 30. The semiconductordevice according to claim 23, wherein said first dopant dose of saidfirst field stop zone is at least about 5×10¹¹ cm⁻².
 31. Thesemiconductor device according to claim 23, wherein said first fieldstop zone has a depth of penetration that is less than about 1 μm withrespect to said second main surface.
 32. The semiconductor deviceaccording to claim 23, further comprising: a metal layer pattern formedon said first main surface and a backside metallisation connected tosaid second main surface of said semiconductor substrate.
 33. Thesemiconductor device according to claim 23, comprising an insulated gatebipolar transistor.
 34. A diode junction in a semiconductor devicesubstrate, comprising: a first semiconductor layer of a firstconductivity type; a second semiconductor layer of a second conductivitytype forming a junction with the first semiconductor layer; a firstfield stop zone of said first conductivity type defined by implantedfirst dopant atoms of a first dopant concentration within said firstsemiconductor layer; and a second field stop zone of said firstconductivity type defined by implanted protons of a second dopantconcentration within said first semiconductor layer, said first atomshaving an energy level that is at least 0.15 eV below the energy levelof the conduction band edge of said first semiconductor layer,respectively.
 35. The diode junction according to claim 34, wherein saidfirst field stop zone is defined by implanted selenium atoms.
 36. Thediode junction according to claim 34, wherein said first field stop zoneis defined by implanted sulphur atoms.
 37. The diode junction accordingto claim 34, wherein said first field stop zone is defined by implantedselenium or sulphur atoms, respectively, combined with implantedphosphorus or arsenic atoms, respectively.
 38. The diode junctionaccording to claim 37, wherein the ratio between selenium or sulphuratoms, respectively, and phosphorus or arsenic atoms, respectively, iswithin the range between 0.15 and 0.8, preferably between 0.3 and 0.7.39. A semiconductor device comprising: a semiconductor substrate of afirst conductivity type; an implantation zone pattern implanted througha surface of the substrate; an emitter zone of a second conductivitytype formed adjacent to said surface; and a field stop zone of saidfirst conductivity type, defined by first and second dopant atoms andformed adjacent to said emitter zone in said semiconductor substratewith a depth of penetration that is less than 1 μm with respect to saidsurface, at least part of said first dopant atoms having an energy levelthat is at least 0.15 eV below the energy level of the conduction bandedge of said semiconductor substrate, said second dopant atoms acting asshallow impurities.
 40. The semiconductor device according to claim 39wherein the semiconductor device is an insulated gate bipolartransistor.